Ubiquitous order-disorder transition in the Mn antisite sublattice of the (MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_n$ magnetic topological insulators
Adv. Sci. 2024, 11, 2402753 Magnetic topological insulators (TIs) herald a wealth of applications in spin-based technologies, relying on the novel quantum phenomena provided by their topological properties. Particularly promising is the (MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_n$ layered family of establishe...
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Zusammenfassung: | Adv. Sci. 2024, 11, 2402753 Magnetic topological insulators (TIs) herald a wealth of applications in
spin-based technologies, relying on the novel quantum phenomena provided by
their topological properties. Particularly promising is the
(MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_n$ layered family of established intrinsic
magnetic TIs that can flexibly realize various magnetic orders and topological
states. High tunability of this material platform is enabled by
manganese-pnictogen intermixing, whose amounts and distribution patterns are
controlled by synthetic conditions. Positive implication of the strong
intermixing in MnSb$_2$Te$_4$ is the interlayer exchange coupling switching
from antiferromagnetic to ferromagnetic, and the increasing magnetic critical
temperature. On the other side, intermixing also implies atomic disorder which
may be detrimental for applications. Here, we employ nuclear magnetic resonance
and muon spin spectroscopy, sensitive local probe techniques, to scrutinize the
impact of the intermixing on the magnetic properties of
(MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_n$ and MnSb$_2$Te$_4$. Our measurements not
only confirm the opposite alignment between the Mn magnetic moments on native
sites and antisites in the ground state of MnSb$_2$Te$_4$, but for the first
time directly show the same alignment in (MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_n$
with n = 0, 1 and 2. Moreover, for all compounds, we find the static magnetic
moment of the Mn antisite sublattice to disappear well below the intrinsic
magnetic transition temperature, leaving a homogeneous magnetic structure
undisturbed by the intermixing. Our findings provide a microscopic
understanding of the crucial role played by Mn-Bi intermixing in
(MnBi$_2$Te$_4$)(Bi$_2$Te$_3$)$_n$ and offer pathways to optimizing the
magnetic gap in its surface states. |
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DOI: | 10.48550/arxiv.2402.06340 |